Control device for fuel supply in internal combustion engines

ABSTRACT

In a device wherein a solenoid valve is located at an inlet stub of each cylinder of an internal combustion engine and wherein a time width of a current to be supplied to the solenoid valves is controlled thereby to control the amount of fuel to be supplied to each cylinder, a high current is caused to temporarily flow through an electromagnetic winding at a moment when the solenoid valve is intended to be opened, while thereafter the current flowing through the electromagnetic winding is reduced to a holding current of the solenoid valve (or a slightly higher current than the holding current) whereby the response of the solenoid valve upon closure is improved.

United States Patent Suda [4 Aug. 8, 1972 CONTROL DEVICE FOR FUEL SUPPLY 3,021,454 2/l962 Pickens.................3 l 7/DlG. 4 IN INTERNAL COMBUSTION ENGINES 3,240,191 3/1966 Wallis 1 23/32 EA 72 l t Se Such, l-l'ta hi, .I l 1 or w l c apan Primary Examiner-Laurence M. Goodridge [73] Assignee: Hitachi, Ltd., Tokyo, Japan 458mm Flint [22] Filed; April 1, 1970 Attorney-Craig, Antonelli & Hill [21] Appl. No.: 24,759 30 F A on D. In a device wherein a solenoid valve is located at an 1 W my inlet stub of each cylinder of an internal combustion April 2, 1969 Japan ..44/24763 engine and wherein a time width of a current to be supplied to the solenoid valves is controlled thereby to [52] US. Cl. .113/32 EA, 3 l 7/DIG. 4 control the amount of fuel to be supplied to each [5 I] IIIL CI. 3/00, F02! 51/00 cylinder, 3 high current is caused to temporarily flow M O EA, I 4 through an electromagnetic at a moment when the solenoid valve is intended to be opened, [56] Rdmm CM while thereafter the current flowing through the elec- IT TE tromagnetic winding is reduced to a holding current of UN ED S PATENTS the solenoid valve (or a slightly higher current than 2,934,050 4/1960 Pnbble ..l23l32 EA the holding cur-rem) whereby the response f the sole 3 n3 4 uwn 2,317,888 4/1943 Gieffers................3l7/DIG.4 2,886,015 5/[959 Steinke l23/32 EA 8 China, 7 [having Figures PATENTEDAUG 8 m2 3.682.144

F 6T FIG 2a PRIOR ART 60/1/0110 77%? c Cur OFF 6 5 3 FIG 2b V F/G 4 s u t b IN 'ENTOR ATTORNEY CONTROL DEVICE FOR FUEL SUPPLY IN INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device of the fuel supply system for internal combustion engines. More particularly, the invention resides in improving the performance characteristics of solenoid valves used as controlling means, thereby permitting a highly precise control of the fuel supply.

2. Description of the Prior Art In the control device of a fuel supply system of the fuel injection type, a fuel injection nozzle is located at each inlet stub of an internal combustion engine, whereby the amount of fuel to be injected from the injection nozzle is controlled by means of a controlling valve.

Since the amount Q of fuel to be injected is expressed as a product between a flow rate 3 (per unit time) and a period of time t, the control of the fuel amount Q may be effected by varying the flow rate g and/or the period of time t. The control may be realized through variation of the amount of release and/or the opening time of the controlling valve.

The controlling valve is classified into the mechanical control type and the electromagnetic control type (a solenoid valve), and the latter is more advantageous for apparatus which determine the amount of fuel to be supplied to internal combustion engines depending upon the conditions.

This is because such an apparatus may be easily realized by detecting the various conditions in the form of electrical signals and operating them with an electrical operational unit, thereby controlling a current flowing through an electromagnetic winding or coil.

In addition, the control by means of the electromagnetic valve is easier with variations in the time width of opening time than with those in the amount of the opening. There has therefore been generally employed a method according to which the electrical signals are operated to provide a pulse-shaped drive voltage of a desired time width, which is then impressed upon the electromagnetic coil to change the opening time width of the valve.

In the actual control, the rate of variations in the amount of fuel is of a very small value. Therefore, in order to precisely control the amount, a small flow rate 3 and a large time width 1 are more advantageous.

However, the initiation of the opening of the electromagnetic valve is often controlled so as to enable fuel to be injected during a period in which a suction valve is opened in synchronism with the rotation of a crank-shaft of an internal combustion engine. An excessive opening time width 2 is therefore not desirable.

Furthermore, the excessive opening time width t poses a problem in that it may possibly overlap the subsequent injection.

In addition, the electromagnetic valve exhibits an opened moment which lags over the pulse-shaped drive voltage applied to the electromagnetic coil, and hence this delay time should also be taken into consideration. As a result, the maximum opening time width 1,, becomes an extremely small value.

SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a device which broadens the opening time width 1 of a solenoid valve under the above-mentioned restrictive conditions, thereby permitting a highly precise fuel control.

A feature of the invention resides in that there are shortened both a delay time measuring from the impression of a drive voltage upon an electromagnetic coil of the solenoid valve to the completion of the opening of the valve and a delay time measuring from the removal of the drive voltage to the closure of the valve, with the result that a wider control of the maximum opening time width r is made possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram of a prior art electrical connection conventionally used in driving a solenoid valve;

FIGS. 2a and 2b are waveform diagrams of voltages at the drive of a solenoid valve;

FIG. 3 is an electrical connection diagram showing an embodiment of the present invention;

FIG. 4 is a diagram of a current characteristic curve in the embodiment shown in FIG. 3; and

FIGS. 5 and 6 are electrical connection diagrams respectively showing further embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of the embodiments of the invention, reference will be made to a prior art electrical circuit arrangement as shown in FIG. 1, which has been used in driving a solenoid valve.

The circuit arrangement comprises a series circuit connected to a terminal 1 of a power source and consisting of an electromagnetic coil 2, a resistor 3 and the emitter-collector circuit of a transistor 4 for control, and a signal circuit having the base of the transistor 4 connected through a resistor 5 to a signal input terminal 6.

When in such an electrical circuit arrangement a bias voltage is impressed upon the signal input terminal 6 thereby to control the internal resistance across the emitter and collector of the transistor 4, a current is caused to flow through the electromagnetic coil 2 which may be controlled to operate the opening and closure of the solenoid valve.

when the input terminal 6 of the transistor 4 is supplied with a drive voltage as shown in FIG. 2a, the terminal voltage V of the electromagnetic winding 2 varies as illustrated in FIG. 2b.

Observing this curve, an inflection point is seen therein at a moment Td, after the application of a drive voltage.

This is caused by the fact that the current flowing through the electromagnetic coil 2 increases with a time constant, which is determined by the inductive reactance L as well as winding resistance r of the electromagnetic coil 2 itself and the resistance R of the external resistor 3, to accordingly increase an electromagnetic force, with the result that a plunger to operate the valve is moved and the permeance of the magnetic circuit is thereby changed.

Accordingly, this moment is the instant at which the opening of the valve is completed, and the period of time Td is the delay time in opening the electromagnetic valve.

When the drive voltage is thereafter removed from the electromagnetic coil 2, the current flowing therethrough will be cut off. Then a counter electromotive force appears in dependence upon the cutoff speed and the magnitude of the current having been flowing through the electromagnetic coil 2, and the voltage produced is attenuated in a period of time Td; which is determined by the collector leakage current of the transistor 4 and other leakage currents.

The terminal voltage V of the electromagnetic coil 2 is slowly attenuated thereafter.

Variations in this region are caused by demagnetization of magnetic materials included in the magnetic circuit, and the terminal voltage V is damped following the speed of demagnetization.

The curve is observed to have another inflection point at a moment at which a period of time Td, has elapsed after removal of the drive voltage. The inflection point is due to a variation in the permeance which in turn is caused by the fact that energy in the magnetic circuit decreases to reduce the attractive force whereby the plunger has been reset.

Accordingly, this moment is the instant at which the closure of the solenoid valve is finished, and the period of time Td is the closure delay time.

Such two delay times as mentioned may be shortened by improving the magnetic material, but such an improvement is subject to limitations.

In order to make shorter the delay times, a method has hitherto been employed in which a high and pulseshaped auxiliary voltage is superposedly impressed from a separate circuit in the region where the opening is initiated, whereby the delay at the opening is shortened. However, no satisfactory results have been obtained.

This is because the method only increases the voltage at the initiation of opening the valve, so that even if it may really reduce the opening delay time, it has never been capable of improving the closure delay time.

The present invention makes the two delay times still shorter through an appropriate control of a current flowing through the electromagnetic coil.

An embodiment shown in FIG. 3 realizes the reduction in the time delay by connecting a capacitor 7 in parallel with the resistor 3.

The respective values of the circuit elements are determined such that when the transistor 4 is brought into the conductive state, a steady current caused to flow through the electromagnetic coil 2 becomes equal to or slightly higher than a holding current required to maintain the opened state of the electromagnetic valve, and in addition, a current caused to flow through the electromagnetic coil 2 in the process of a transient phenomenon and dependent upon the inductive reactance L as well as winding resistance r of the coil 2, the value R of the resistor 3 and the value C of the capacitor 7 becomes larger than the opening current of the solenoid valve, this transient phenomenon being non-oscillatory.

With such an electrical circuit arrangement, upon bringing the transistor 4 into the conductive state, a

large current is caused to flow, as shown in FIG. 4, through the electromagnetic coil 2 via the capacitor 7 in the last region, whereby the electromagnetic valve is opened. Thereafter, charging of the capacitor 7 is completed, so that a holding current of the electromagnetic valve is caused to flow via the resistor 3.

Accordingly, at the initiation of the opening of the solenoid valve, a large current flows to shorten the opening delay time.

On the other hand, at the initiation of the closure of the solenoid valve, the current which is flowing through the electromagnetic coil 2 is small, hence a counter electromotive force which takes place, due to the current interruption, is feeble and the damping thereof is effected in a short period of time, so that the closure delay time Td can be remarkably shortened.

An experiment with an electromagnetic valve which has an electromagnetic coil 2 wherein L 4mI-l and r 2.00, showed the following results:

R C Td Td,

(not in- Prior Art 4.5!] eluded) 2.0ms 2. 3ms Invention (I) 16.60 I00 pF l.9rns 1.6ms (2) 16.60 200 uF 1.8ms l.6ms

In addition, such control may be similarly effected by using a transistor circuit connected across the resistor 3 in place of the capacitor 7. Control is also possible by controlling the internal resistance across the emitter and collector electrodes of the transistor 4.

Referring to FIG. 5, description will be made of a further embodiment in which use is made of the abovementioned transistor circuit including a capacitor.

In FIG. 5, the resistor 3 is connected in parallel with the emitter-collector circuit of a transistor 8, the base electrode of which is connected to the input terminal 6 through a resistor 9 and a capacitor 7'.

There is provided a diode 10 for discharging charges in the capacitor 7 There will now be described a case wherein in the above arrangement, the input terminal 6 is impressed with a positive pulse-shaped signal voltage as illustrated in FIG. 2a.

First, since the base-emitter circuit of the transistor 4 is biased in the forward direction in this case, the emitter-collector circuit of the transistor 4 is brought to the conductive state. Since the terminal voltage of the capacitor 7' is not charged in the initial region, the signal voltage is simultaneously biased in the forward direction, the base-emitter circuit of the transistor 8 through the capacitor 7 and the resistor 9, thereby bringing the emitter-collector circuit of the same to the conductive state.

Accordingly the current caused to flow into the electromagnetic coil 2 from the power source terminal 1 comes to pass through the emitter-collector circuits of both the transistors 8 and 4.

The impedance of this current circuit is of a low value due to the inductive reactance L as well as the winding resistance r of the electromagnetic winding 2, and hence the current is high and quickly completes the opening of the electromagnetic valve.

The capacitor 7', after a current has flowed therethrough for a predetermined period of time, has its terminal voltage raised, so that the base current of the transistor 8 is reduced. Therefore the internal resistance across the emitter and collector circuit thereof is increased, with the result that the current flowing through the electromagnetic coil 2 is decreased. When the transistor 8 reaches the non conductive state, the current which flows through the electromagnetic coil 2 will be reduced to a holding current determined by the winding resistance r of the coil 2 and the resistance R of the resistor 3.

When the signal voltage having been impressed upon the input terminal 6 is removed after the lapse of a predetermined period of time, the emitter-collector circuit of the transistor 4 will become non-conductive and the current flowing through the electromagnetic coil 2 will also be cut off. Since the current flowing through the electromagnetic coil 2 at this moment is the holding current which is relatively small, the counter electromotive force is small and consequently the solenoid valve is rapidly reset. Simultaneously, charges stored in the capacitor 7' are discharged through the low impedance of the diode 10 in the forward direction, and preparations are made for the subsequent operation.

A still further embodiment shown in P10. 6 has the capacitor 7' connected in parallel with the base resistor 5 of the transistor 4. The resistance of the resistor 5 is set so that the collector current of the transistor 4 may be made the holding current of the electromagnetic valve by means of a signal voltage to be impressed upon the input terminal 6. The capacitance of the capacitor 7' is set so that such a high current that the collector current of the transistor 4 can open the solenoid valve as quickly as possible, may be caused to flow through the capacitor 7' during a very short period of time between impression of the signal voltage and opening of the solenoid valve.

It will be understood that such an embodiment may shorten the delay in operation of the electromagnetic valve in the same way as in the previous embodiments.

As described above, according to the invention, a large current is caused to flow through an electromagnetic coil at the initiation of the opening of an electromagnetic valve thereby to quickly complete the opening, while thereafter the current is interrupted after being once reduced to a holding current, with the result that particularly the time delay may be conspicuously shortened.

Accordingly, the electromagnetic valve may be satisfactorily controlled even when the opening time width 1 is made relatively large, thus permitting a highly precise control of the fuel supply.

I claim:

1. A control circuit for controlling the supply of fuel in an internal combustion engine, including a solenoid valve for controlling the amount of fuel to be supplied to the internal combustion engine through the flow of current through the electromagnetic winding of said solenoid valve, one side of said winding being connected to a source of supply voltage over a predetermined period of time, said circuit comprising:

an input terminal for supplying a control signal having a prescribed duration extending from a first portion for initiating the fiow of current through said winding to a second portion for terminating the flow of current through said winding, the duration of said current flow through said winding controlling the length of time that said solenoid valve is energized, to thereby effect the supply of fuel to said engine over said predetermined period of time;

switching means, coupled between said input terminal and said winding, for switching into said winding a current from said source of supply voltage in response to said control signal, the amplitude of said control signal over said prescribed duration being sufficient to energize said switching means; and

means, coupled to said switching means, for substantially shortening any delay time existing between the flow and cut-off of current of a sufficient magnitude to energize said winding, so as to effect the supply of fuel to said engine, including circuit means for supplying a substantially large current to said winding in response to said first portion of said control signal, so as to energize said valve winding to open said valve, and for reducing the counterelectromotive force in said winding upon the occurrence of said second portion of said control signal and for maintaining the supply of current of a sufficient magnitude to keep said winding energized prior to said second portion of said control signal, wherein said switching means comprises a first transistor, a first electrode of which is resistively connected to said solenoid winding, a second electrode of which is connected to a reference potential and a third electrode of which is resistively connected to said input terminal and wherein said circuit means comprises a capacitor connected in parallel with the resistive connection of one of said electrodes of said first transistor.

2. A circuit according to claim 1, wherein said circuit means comprises a capacitor connected in parallel with the resistive connection of said first electrode of said first transistor with said solenoid winding.

3. A circuit according to claim 1, wherein said circuit means comprises a capacitor connected in parallel with a resistive connection of said third electrode of said first transistor with said input terminal.

4. A circuit according to claim 2, wherein said first electrode of said first transistor is the collector electrode thereof, said second electrode is the emitter electrode thereof, and said third electrode is the base electrode thereof.

5. A circuit according to claim 3, wherein said first electrode of said first transistor is the collector electrode thereof, said second electrode is the emitter electrode thereof, and said third electrode is the base electrode thereof.

6. A control circuit for controlling the supply of fuel in an internal combustion engine, including a solenoid valve for controlling the amount of fuel to be supplied to the internal combustion engine through the flow of current through the electromagnetic winding of said solenoid valve, one side of said winding being connected to a source of supply voltage over a predetermined period of time, said circuit comprising:

an input terminal for supplying a control signal having a prescribed duration extending from a first portion for initiating the flow of current through said winding to a second portion for terminating the flow of current through said winding, the duration of said current flow through said winding controlling the length of time that said solenoid valve is energized, to thereby effect the supply of fuel to said engine over said predetermined period of time;

switching means, coupled between said input termeans coupled to said switching means for substantially shortening any delay time existing between the flow and cut-off of current of a sufficient magnitude to energize said winding, so as to effect the supply of fuel to said engine, including circuit means for supplying a substantially large current to said winding in response to said first portion of said control signal, so as to energize said valve winding to open said valve, and for reducing the counterelectromotive force in said winding upon the occurrence of said second portion of said control signal and for maintaining the supply of current of a sufficient magnitude to keep said winding energized prior to said second portion of said control signal, wherein said switching means comprises a first transistor, a first electrode of which is resistively connected to said solenoid winding, a second electrode of which is connected to a reference potential and a third electrode of which is resistively connected to said input terminal, wherein said circuit means comprises a second transistor having first and second electrodes thereof connected across the resistive connection between said first electrode of said first transistor and said solenoid winding and a third electrode thereof capacitively coupled to said input terminal.

7. A circuit according to claim 6, wherein said circuit means comprises a resistor-capacitor series connection between said third electrode of said second transistor and said input terminal, and a diode connected between a junction of said resistor and capacitor connected in series forming said series connection, and said reference potential.

8. A circuit according to claim 7, wherein said first, second and third electrodes of said second transistor are the collector, emitter and base electrodes thereof, respectively. 

1. A control circuit for controlling the supply of fuel in an internal combustion engine, including a solenoid valve for controlling the amount of fuel to be supplied to the internal combustion engine through the flow of current through the electromagnetic winding of said solenoid valve, one side of said winding being connected to a source of supply voltage over a predetermined period of time, said circuit comprising: an input terminal for supplying a control signal having a prescribed duration extending from a first portion for initiating the flow of current through said winding to a second portion for terminating the flow of current through said winding, the duration of said current flow through said winding controlling the length of time that said solenoid valve is energized, to thereby effect the supply of fuel to said engine over said predetermined period of time; switching means, coupled between said input terminal and said winding, for switching into said winding a current from said source of supply voltage in response to said control signal, the amplitude of said control signal over said prescribed duration being sufficient to energize said switching means; and means, coupled to said switching means, for substantially shortening any delay time existing between the flow and cut-off of current of a sufficient magnitude to energize said winding, so as to effect the supply of fuel to said engine, including circuit means for supplying a substantially large current to said winding in response to said first portion of said control signal, so as to energize said valve winding to open said valve, and for reducing the counter-electromotive force in said winding upon the occurrence of said second portion of said control signal and for maintaining the supply of current of a sufficient magnitude to keep said winding energized prior to said second portion of said control signal, wherein said switching means comprises a first transistor, a first electrode of which is resistively connected to said solenoid winding, a second electrode of which is connected to a reference potential and a third electrode of which is resistively connected to said input terminal and wherein said circuit means comprises a capacitor connected in parallel with the resistive connection of one of said electrodes of said first transistor.
 2. A circuit according to claim 1, wherein said circuit means comprises a capacitor connected in parallel with the resistive connection of said first electrode of said first transistor with said solenoid winding.
 3. A circuit according to claim 1, wherein said circuit means comprises a capacitor connected in parallel with a resistive connection of said third electrode of said first transistor with said input terminal.
 4. A circuit according to claim 2, wherein said first electrode of said first transistor is the collector electrode thereof, said second electrode is the emitter electrode thereof, and said third electrode is the base electrode thereof.
 5. A circuit according to claim 3, wherein said first electrode of said first transistor is the collector electrode thereof, said second electrode is the emitter electrode thereof, and said third electrode is the base electrode theReof.
 6. A control circuit for controlling the supply of fuel in an internal combustion engine, including a solenoid valve for controlling the amount of fuel to be supplied to the internal combustion engine through the flow of current through the electromagnetic winding of said solenoid valve, one side of said winding being connected to a source of supply voltage over a predetermined period of time, said circuit comprising: an input terminal for supplying a control signal having a prescribed duration extending from a first portion for initiating the flow of current through said winding to a second portion for terminating the flow of current through said winding, the duration of said current flow through said winding controlling the length of time that said solenoid valve is energized, to thereby effect the supply of fuel to said engine over said predetermined period of time; switching means, coupled between said input terminal and said winding, for switching into said winding a current from said source of supply voltage in response to said control signal, the amplitude of said control signal over said prescribed duration being sufficient to energize said switching means; and means coupled to said switching means for substantially shortening any delay time existing between the flow and cut-off of current of a sufficient magnitude to energize said winding, so as to effect the supply of fuel to said engine, including circuit means for supplying a substantially large current to said winding in response to said first portion of said control signal, so as to energize said valve winding to open said valve, and for reducing the counter-electromotive force in said winding upon the occurrence of said second portion of said control signal and for maintaining the supply of current of a sufficient magnitude to keep said winding energized prior to said second portion of said control signal, wherein said switching means comprises a first transistor, a first electrode of which is resistively connected to said solenoid winding, a second electrode of which is connected to a reference potential and a third electrode of which is resistively connected to said input terminal, wherein said circuit means comprises a second transistor having first and second electrodes thereof connected across the resistive connection between said first electrode of said first transistor and said solenoid winding and a third electrode thereof capacitively coupled to said input terminal.
 7. A circuit according to claim 6, wherein said circuit means comprises a resistor-capacitor series connection between said third electrode of said second transistor and said input terminal, and a diode connected between a junction of said resistor and capacitor connected in series forming said series connection, and said reference potential.
 8. A circuit according to claim 7, wherein said first, second and third electrodes of said second transistor are the collector, emitter and base electrodes thereof, respectively. 